There aren't many "less traveled" roads here but there are quite a few group rides around town.

The Trek Store in Mt Pleasant probably does the most remote type ride and their Saturday rides leave from the store and go north towards Francis Marion National forest. They offer a 65 mile A ride (speeds of 23-30) at 7:00 and a 52 mile B ride at 7:30 (speeds from 18-22). They also have a ride on Thursday called the Death March. I've never tried it but I hear it's around 40 miles and close to 30 mph the whole way.

Try Sports Mt Pleasant has a Tuesday ride that leaves from the shop at 6:00 and goes through Sullivans Island and Isle of Palms that is 24 miles and breaks up into an A and B group. It's for all levels of rider and it's a nice ride. They also have a Sunday 40 miler at 8:00 that hits all the bridges.

Charleston Bicycle Co has Tuesday and Thursday rides that meet in West Ashley/Johns Island too. I think they meet at Osaka at 6:00.

If you google coastal cyclists you can find some ride routes, links to local shops and a ride calendar. Feel free to PM me if you have any specific questions.